Located in far northwest Sonora, Mexico, the Pinacate volcanic field comprises a 1,500 km2 area of Pleistocene lava flows with over 400 cinder cones and 8 maars. The volcanoes in the Pinacate are monogenetic—meaning they erupt only once and each have a unique magmatic signature. The field today is part of El Pinacate and Gran… Continue reading Pinacate Volcanic Field
Located just north of Flagstaff, Arizona, the San Francisco volcanic field comprises an area of 1,800 sq miles and contains around 600 volcanoes. These volcanoes range in age from 6 million years old to less than 1,000 years old. Given their location on the Colorado Plateau, many volcanoes have experienced little erosion (like SP Crater… Continue reading San Francisco Volcanic Field
Tephra with iridescent blue colors from the Pinacate Volcanic Field in Sonora, Mexico Image by author
Looking at the two images above, they appear quite similar: both are of very large (~1 mile wide), nearly perfectly circular craters in the ground. However, one was formed by a meteorite impact and the other is a maar formed by an explosive volcanic eruption. Think you can figure out which one is which? From just… Continue reading Meteorite Impact or Maar?
Mars is home to Olympus Mons (pictured above), the largest volcano in the solar system. Rising 21-24 km from the surrounding area, Olympus Mons is the dominant spot in the Tharsis region, which is the largest topographic feature on the planet. The Tharsis volcanic province covers close to 25% of the planet’s surface and houses… Continue reading Volcanism on Mars
Volcanic glass - rapid cooling causes minimum crystal growth, which creates a glassy texture
Scoria is an extrusive igneous rock formed during volcanic eruptions. It is highly vesicular, meaning that it has many cavities (vesicles) both inside and at its surface. It has a very low density, so for a rock, it’s pretty darn light! Image by author
Welded tuff is a type of pyroclastic rock. A pyroclastic deposit consists of fragmented material that is formed from explosive volcanic activity or from aerial expulsion from a volcanic event. These pyroclasts may be deposited in the form of pyroclastic flows [a dense, ground-hugging cloud of ashy material], forming ignimbrites (Greek for “fire cloud material”).… Continue reading Welded Tuff
Rhyolite is an igneous, extrusive volcanic rock high in silica forming typically in continental arc settings. The flow-banding in this sample is caused by the friction of the viscous magma in contact with a solid rock surface or by compaction, causing flattening and welding of shards and pummice. [Be prepared for pictures of a bunch… Continue reading Flow-banded rhyolite
Horseshoe Harbor near Marquette, MI Midcontinent rift, baby! Just look at all these volcanic rocks.